Printing forms of high polymer substances



y 1956 H. HAYDN ETAL 3,250,616

PRINTING FORMS OF HIGH POLYMER SUBSTANCES Filed Oct. 31. 1961 Support 1 T. -t- 7E j layer 4 H Transfer layer" Support 5 was ed and developed areas P if [at all lv J revel sedfiiirztgg L V 2 Transferred ar-ti n5 6 of fize fmnsfefi Zaygr4 7 Negative nanlater'allz 4 reversed pruztz'rgg 3 form. R sidual portions f the transfer laye14 511 to t e 1" 7 ea E 7 5 r 3 Negaiive lafgzrally fi rsed pruztu fornz I 5 INVENTORS H Lld egard H aydm Edith Wey oLe United States Patent 3,250,616 PRINTING FORMS OF HIGH POLYMER SUBSTANCES Hildegard Haydn and Edith Weyde, Leverkusen, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany Filed Oct. 31, 1961, Ser. No. 148,844 Claims priority, application Germany, Nov. 16, 1960, A $6,044 Claims. (Cl. 96-49) This invention relates to printing forms of high polymer substances as well as to a process for the production of said forms by means of the silver salt diffusion process.

There are a number of well-known photographic processes of producing printing forms.

These methods include in particular the process of differentially hardening silver salt emulsion layers and transferring unhardened strata of such layers to a support to obtain useful printing forms. The binding agents of these layers are in general gelatin. It is also known, however, to replace the gelatin partially or completely by other polymeric substances or synthetic film-forming compounds that are capable of being tanned.

In this. connection the silver salt diffusion process has already been used.

It is among the objects of the present invention to provide a novel method for producing printing forms by means of the silver salt diffusion process, whereby the differential hardening is obtained without the use of a hardening agent, thus providing printing forms with excellent physical properties. Other objects will be apparent from the following description.

We have found that film-forming polymeric natural or synthetic compounds containing carboxyl radicals or COOX radicals in Which X is a metal that are capable of reacting with silver ions to form polymeric silver salts serve as very useful binding agents for the transfer layers or printing matrix layers for the production of printing forms. By the formation of the silver salt the structure and the swelling properties of these polymeric compounds are changed in such a way that these areas become insoluble in water and have an imagewisely differentiated adhesiveness of that high polymeric substance of the transfer layer to other materials.

According to a preferred embodiment of our invention, the adhesiveness of the transfer layer to the non-lightstruck or unexposed areas of the negative silver halide emulsion layer can be improved by treating the negative layer with a solution containing development nuclei, preferably nuclei of metallic silver which are colloidally distributed therethrough or to add such nuclei or products that are capable of forming such nuclei on the surface of the negative to the developer solution. Thus it is possible to transfer these parts which have been entirely or partly converted into silver salt to another support by tearing out.

High polymer substances having carboxyl groups which are particularly suitable for forming this layer include natural or processed natural products such as carboxymethyl cellulose, alginic acid and alginates and its derivatives and pectins. These compounds are chemically characterized in so far as they belong to the class of the carbohydrates having cyclic structures in particular of the pyranoside type substituted by a carboxyl grouping either directly at the ring or at a side chain. Thus the compounds contain approximately 10-50 percent, preferably -30 percent carboxyl groups per cyclic unit.

Carboxyznethyl cellulose and processes for its preparation and structure are described by W. F. Waldeck and F. W. Smith, in Industrial and Engineering Chemistry, vol 44, pages 2803 to 2812 (December 1952), which was azsrrt Patented May 10, 1966 reprinted in collaboration with Rodney N. Hader in Modern Chemical Processes, which are volumes containing a series of articles describing chemical manufacturing plants by the editors of Industrial and Engineering Chemistry, III, pages 132 to 141, published by Reinhold Publishing Corporation, New York, 1954. Alginates or pectinic acid which are suitable for the process according to the invention are disclosed for example in Recent Advances in Organic Chemistry by Alfred W. Stewart and Hugh Graham, vol. II, pages 117118, published by Longmans Green & Co., London, 7th ed., 1948 (Chapter IV, part B, entitled Alginic Acid), and in Alginsauve und Alginate by H. Maas, SCT-Verlagesgesellchaft, Heidelberg, 1959, in particular pages 24 et seq., furthermore Chemische Textilfasern, Folien und Filme by G. Pummerer, F. Enke Verlag, Stuttgart, 1953, pages 549 et seq.

Furthermore, synthetic resins containing carboxyl groups maybe used, such as polymers of acrylic acid, maleic acid with a content of at least 20 percent of the acidic compound and similar substances that are capable of forming silver salts, furthermore, condensation products of formaldehyde with phenoxy acetic acid or other modified phenol formaldehyde resins containing carboxyl groups.

These polymeric products can be used in admixture with other film-forming polymers such as polyvinyl alcohols, gelatin, starch or starch derivatives and the like.

The transfer layer according to our invention may be prepared by casting a solution of the high polymer substance onto a paper carrier covered with hardened gelatin so that the polymeric substance does not penetrate into the paper support. The processes and printing forms of the present invention are described in the following general example:

A layer of carboxymethyl cellulose is cast onto a sheet of paper having a layer of hardened gelatin or other filmforming substance that produces a smooth surface. This transfer sheet consisting of the paper support and a transfer layer of carboxyl methyl cellulose is brought into contact with a negative silver halide emulsion layer that had been exposed to the object to be reproduced, after either layer has been moistened with a developer solution containing a solvent for silver halides. The light-struck areas of the negative are thereby reduced to silver while the silver halides of the non-light-struck areas are dissolved and transferred into the corresponding areas of the carboxymethyl cellulose layer, forming thereby polymeric silver salts and accordingly changing the chemical properties of these areas as described above, so that those areas which correspond to the non-light-struck areas of the negative layer have a greater adhesiveness to the negative layer than to the underlying layer of hardened gelatin. If these two materials are now separated, the reacted portions of the carboxymethyl cellulose layer are present as a relief on the non-light-struck areas of the negative layer because the carboxymethyl cellulose layer at these areas has been torn out right down to the layer of hardened gelatin. At the same time, a relief is thereby formed on the carboxymethyl cellulose layer, wherein the depressions correspond to the original image. Both the relief formed on the negative layer and that remaining on the transfer layer may be used as a printing form.

The process of the present invention is also illustrated in and may be described by reference to the accompanying drawing, in FIG. 1 of which is represented a conventional light-sensitive negative sheet that consists of a support 1 to which adheres a layer of a light-sensitive silver-halide emulsion 2 and a separate transfer sheet that consists of a support 3 upon which is deposited a transfer layer 4 consisting of carboxymethylcellulo-se or the completion of the development, the transfer layer 4 of the transfer sheet is brought into contact with the wet silver-halide emulsion layer 2. During the development, a silver image is formed in the exposed areas of the emulsion layer 2, as represented in FIG. 2, while the silver halide remaining in the unexposed areas of the emulsion layer 2 is dissolved by the silver halide solvent and diffuses into adjacent areas of the transfer layer 4 of the transfer sheet.

The developed negative sheet and the transfer sheet are then torn apart (separated) to produce two printing forms, which are represented in FIGS. 3 and 4, and are respectively a positive laterally reversed and a negative nonlaterally reversed printing form. The areas of the transfer layer 4 which are adjacent the unexposed areas of the emulsion layer 2 (which are designated 6 in FIG. 3) adhere firmly to the emulsion'l ayer 2 and are consequently torn out of the transfer layer 4 when the transfer sheet and negative sheet are torn apart.

The positive laterally reversed printing from that is thus obtained, which.is represented in FIG. 3, consists of both the support 1 and emulsion layer 2 of the negative sheet and a relief layer consisting of the torn-out portions 6 of the transfer layer 4 of the transfer sheet.

The negative nonlaterally reversed printing form that is thus also obtained, which is represented in FIG. 4, consists of the support 3 of the transfer sheet and a relief layer consisting of the portions of the original transfer layer 4 (which are desingated 7 in FIG. 4) that were adjacent to the exposed and developed areas 5 of the.

emulsion layer 2 and that were not torn out of the transfer layer 4 when the transfer sheet and negative sheet were torn apart.

From the negative nonlaterally reversed printing form represented in' FIG. 4, a negative latenally reversed printing form can be made by bringing a sheet of tissue paper 8 into contact with the relief layer 7 of the printing form. FIGS. 5 and 6 show the relief layer 7 adhering to the sheet of tissue paper 8 producing on the tissue paper a negative laterally reversed relief layer that is suitable for use in spirit duplicating processes.

The positive laterally reversed printing form (FIG. 3) can be used in spirit duplicating processes to make prints by applying an alcohol-soluble dye to the relief layer. When an alcohol-soluble dye is incorporated originally in the transfer layer 4 of the transfer sheet, the relief layer of the resulting positive laterally reversed printing form can be used without further application of dye in the spirit duplicating process.

Relatively large quantities of other substances may be added to the transfer layer without substantially altering its properties. a dye may be incorporated into these layers. Thus by performing the process in accordance with the description herein of the invention, areas of the carboxymethyl cellulose layer corresponding to areas of the picture and containing relatively large quantities of a dye remain on the unexposed areas of the negative. In that case, a positive but laterally reversed picture of the original is produced on the negative. This negative maybe used as a printing form for various processes depending on the type of dyes added. When using an alcohol-soluble dye in the layer, a larger number of copies can be obtained from the printing form of the negative using the process of spirit printing.

The relief remaining on the carboxymethyl cellulose layer may be used as a printing form for the template printing, for example, by transferring the layer which is still moist onto tissue paper. In that case, the pores of the tissue paper remain opened in those areas corresponding to the picture, whereas in other areas they are occluded by the carboxymethyl cellulose layer. The printing dye or an alcohol-soluble dye can enter a paper carrier only through the open pores of the tissue paper. In that case again, one obtains a positive laterally non-reversed reproduction of the original.

As already mentioned above, a number of dilferent coating agents may be used for the processes of the present invention which are characterized by containing carboxyl radicals that are capable of forming silver salts. A very large variety of substances may be used as additives. The choice of dye is determined by the printing process to be used.

Other additives which may be added to these layers infiuence mainly the swelling properties of the layer, which is important for the adhesiveness to the emulsion layer and to the underlying layer of hardened gelatin. For example, the addition of salts or of fillers which are not capable .of swelling, such as barium sulphate, may have a profound effect on the behaviour of the transfer layer. The salt contentof the developer or an addition of alcohol to the developer may also have a considerable influence on that layer. Principally it is possible to cast the layers directly onto a supporting sheet of paper. Preferably, however, the paper sheet should be coated with an intermediate layer of hardened gelatin, polyvinyl alcohol or other agents that produce a smooth surface. This is advantage-cos since the coating agent is prevented from diffusing or creeping into the material during the casting operation, which would make the subsequent transferring of portions of said layer more dificult. It is important that the transfer layers do not adhere too firmly to the support. Instead of paper, it has also been found satisfactory to use film foils in which case it is sometimes possible to omit the intermediate layer.

Experiments have shown that in each individual case the coating agent, support, and intermediate layer must be exactly adjusted to one another. This selection can be made Without difliculties by those having ordinary skill in the art if the general description herein is followed.

As to the binding agent of the transfer layer it sh-oul be stated that by the term carboxy groups or radicals is to be understood in this connection free carboxyl groups as well as radicals having the formula -CO()X in which X is a metal or othe'rradioal capable of neutralizing the carboxyl radical or replacing the hydrogen atom thereof.

- Both groupings are capable of reacting with silver ions to form the corresponding silver salts.

Example 1 1 liter of a 6.2 percent carboxymethyl cellulose (Phrikolat NV special containing about 40 percent salt) is intimately mixed with 30 grams Victoria Blue (Schultz,

For example, considerable quantities of vol. 1, 7th edition, No. 822). After adding saponine, the solution is cast onto a paper which has previously been coated with polyvinyl alcohol. is then treated, together with a photographic negative layer, preferably in an apparatus which is suitable for development in accordance with the silver salt diffusion process. The development may be performed with a developer which has the following composition:

Water, cc. 1000 Sodium sulphite anhydrous, g. Sodium hydroxide anhydrous, g. l2 Hydroquinone, g. 15 Phenidone (l-phenyl-3-pyrazolidone), g. 0.5 Potassium bromide, g. 1 Sodium thiosulphate, g. 5

The exposed negative and the above-described carboxymethyl cellulose layer are together passed into the apparatus (through two separate slots) and the two layers are separated after about 2 minutes. After separation, the carboxymethyl cellulose dye layer remains only on the non-light-struck areas of the negative. The printing matrix The layer produced or form thus produced is suitable for spirit printing for which the usual printing apparatus may be used. 200 to 300 prints may be obtained from such a printing form.

The negative material was prepared as follows:

A sliver chloride-bromide gelatin emulsion is cast onto a paper support. An intermediate baryta layer may be recommendable in certain cases but is in general not necessary. The silver halide content of the light-sensitive layer, which may be additionally sensitized preferably to the blue and green region of the visible light amounts to 1.8-2.6 g. of silver per square metre. The layer is treated before or after being dried with a 0.5 percent dispersion of colloidally distributed metallic silver in water, thereby providing the surface of the light-sensitive emulsion layer with a small amount of silver nuclei.

Example 2 30 g. of Crystal Violet (Schultz, vol. 1, 7th edition, No. 785) are thoroughly mixed with 100 cc. of a 3 percent wax emulsion and dried. This dye-wax mixture is added to 1 liter of 5.4 percent carboxymethyl cellulose (Phrikolat NV special containing about 40 percent salts) on a paper which has been coated with hardened gelatin and it is then treated as described in Example 1.

Example 3 A 5 percent solution of carboxymethyl cellulose (Henkel G 5006), to which percent of a non-swelling substance such as barium sulphate or titanium dioxide has been added as filler, is cast onto a paper which has a base layer of hardened gelatin. The layer is treated as described in Example 1. When the layer has been pulled off from the negative, it is placed while still wet onto a template of Japan paper or a fine fabric as generally used for wax stencil printing or screen printing. After drying for a short period, the layer adheres to the fibrous base. Since the portions of the carboxymethyl cellulose layer which correspond to the original image to be reproduced adhere to the negative, these parts are not transferred to the template. Thus the printing dye can penetrate through the pores of the material of the template.

Example 4 1 liter of Algipon 778 (of the firm Henkel) 0.9 percent, is mixed with 10 g. of Crystal Violet and g. sodium chloride very thoroughly in a ball mill. The solution is cast onto paper which is covered with a hardened gelatin layer. The layers are treated as described in Example 1.

The present invention lends itself readily to a number of useful modifications in method, materials, apparatus, etc.

For example, the support of the transfer material may be paper with or without any immediate layer of a filmforming agent having a smooth surface, furthermore any film-forming polymer is suitable as a carrier, such as cellulose ester, polycarbonate, polyesters in particular those formed from terephthalic acid and ethylene glycol.

The printing dye may be incorporated into the transfer layer or may be applied in the form of a fatty printing ink to the final printing form. The chemical structure or the properties of the dye are not espectially critical and are selected according to the requirements of the particular printing process in which the printing form is to be used. The same holds true with respect to the light-sensitive negative material which has no particular influence with respect to the process of the instant invention. It is only necessary that the portion of the transfer layer sufiiciently adhere to the negative layer. This object is attained by treating the negative material with a solution or dispersion containing finely distributed particles of heavy metals such as silver, gold or the metals of subgroup VHI of the periodic system and metal sulfides or selenides such as cadmium selenide, silver sulfide or zinc sulfide. These nuclei operate in general as development nuclei and the improvement of the adhesion may probably be caused by a minor precipitation of sliver in the surface of said negative .layer. The concentration of said nuclei necessary for obtaining the effect described above is very small, and is far less than the concentration of said nuclei in a commercial positive paper being used for the silver salt diffusion process, serving in this case for the precipitation of the silver halide which causes from the non-exposed and non-developed areas of the negative material and the formation of the positive image. Thus with the developing times being usual in the silver salt diffusion process no photographically disturbing silver precipitationis obtained at the non-light-struck areas of the negative material.

What is claimed is:

1. A process for simultaneously producing from a single negative (I) a positive laterally reversed printing form and (II) a negative non-laterally reversed printing form which comprises:

(a) exposing imagewise to an object to be reproduced a light-sensitive negative sheet comprising a lightsensitive silver halide layer adhering to a negative sheet supporting layer,

(b) developing the exposed light-sensitive negative sheet in a developer containing a silver halide solvent whereby the silver halide in the exposed areas of the emulsion layer is converted to a silver image and the silver halide in the non-exposed areas of the emulsion layer is dissolved,

(c) bringing the exposed emulsion layer of the negative sheet during development into contact with an amount of development nuclei sufiicient to increase the adhesiveness of a transfer sheet to the emulsion layer but an amount less than that which causes a visible silver precipitation in the transfer sheet, said development nuclei being selected from the group consisting of heavy metals, heavy metal sulfides and heavy metal selenides and into contact with a transfer sheet, said transfer sheet consisting essentially of a transfer layer of a film-forming carboxysubstituted carbohydrate having a pyranoside structure and containing between 10 and 50 percent by weight carboxyl radicals adhering to a transfer sheet supporting layer whereby silver halide dissolved from the unexposed areas of the emulsion layer diffuses imagewise into the transfer layer thereby increasing imagewise the adhesiveness of the transfer layer to the emulsion layer, and

(d) separating the transfer sheet and the negative sheet whereby those portions of the transfer layer which were in contact with the unexposed areas of the emulsion layer now adhere to the emulsion layer and those portions of the transfer layer which were in contact with the exposed areas of the emulsion layer remain adhering to the transfer sheet supporting layer thereby producing (I) a positive laterally reversed printing form comprising the negative sheet and a relief layer of portions of the transfer layer and (II) a negative non-laterally reversed printing form comprising the transfer sheet supporting layer and a relief layer of the remaining portion of the transfer layer.

2. The process according to claim 1 wherein the development nuclei are selected from the group consisting of silver, gold, cadmium selenide, silver sulfide, zinc sulfide and metals of subgroup VIII of the Periodic System.

3. The process according to claim 1 wherein development nuclei are added to the developer prior to development.

4. The process according to claim 1 wherein the lightsensitive negative sheet is treated with a colloidal development nuclei dispersion.

5. The process according to claim 1 wherein the filmfor ming carboxy-substituted carbohydrate is selected from the group consisting of carboxymethylcellulose, pectins, alginic acid and salts of alginic acid.

6.. The process according to claim 1 wherein the filmforming carboxy-substituted carbohydrate is carboxymethyl cellulose.

7. The process according to claim 1 wherein the filmforrning carboxy-substituted carbohydrate is a salt of alginic acid.

8. The process according to claim 1 wherein the transfer layer contains an alcohol soluble dye.

9. A positive laterally reversed printing form comprising a printing form support sheet, a gelatin layer containing a silver image supported on said support sheet and a relief layer carried on and adhering to only those portions of the gelatin layer which contain no silver image, I

said relief layer comprising a film-forming carboxy-substituted carbohydrate having a pyranoside structure and containing between 10 and 50 percent by weight carboxyl radicals.

10. The printing form according to claim 9 wherein the relief layer is selected from the group consisting of carboxymethyl cellulose, pectins, alginic acid and salts of alginic acid.

- 11. The printing form according to claim 9 the relief layer is carboxymethylcellulose.

12. The printing form according to claim 9 wherein the relief layer is a salt ofalginic acid.

13. The printing form according to claim .9 wherein the relief layer contains an alcohol soluble dye.

14. A negative laterally reversed printing form comprising a printing form support sheet and relief layer 'wherein in the form of a negative non-laterally reversed image- References Cited hy the Examiner UNITED STATES PATENTS 2,543,181 1/1951 Land 9629 2,923,623 1/ 1960 Land 9629 3,012,885 12/1961 Abbott et a1. 9635 X 3,043,691 7/1962 Weyde et ai. 9629 FOREIGN PATENTS 730,349 5/ 1955 Great Britain.

758,627 10/ 1956 Great Britain.

811,579 4/1959 Great Britain.

821,507 10/1959 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

LOUISE P. QUAST, Examiner.

A. D. RICCI, Assistant Examiner. 

1. A PROCESS FOR SIMULTANEOUSLY PRODUCING FROM A SINGLE NEGATIVE (I) A POSITIVE LATERALLY REVERSED PRINTING FORM AND (II) A NEGATIVE NON-LATERALLYR EVERSED PRINTING FORM WHICH COMPRISES: (A) EXPOSING INAGEWISE TO AN OBJECT TO BE REPRODUCED A LIGHT-SENSITIVE NEGATIVE SHEET COMPRISING ALIGHTSENSITIVE SILVER HALIDE LAYER ADHERING TO A NEGATIVE SHEET SUPPORTING LAYER, (B) DEVELOPING THE EXPOSED LIGHT-SENSITIVE NEGATIVE SHEET IN A DEVELOPER CONTAINING A SILVER HALIDE SOLVENT WHEREBY THE SILVER HALIDE IN THE EXPOSED AREAS OF THE EMULSION LAYER IS CONVERTED TO A SILVER IMAGE AND THE SILVER HALIDE IN THE NON-EXPOSED AREAS OF THE EMULSION LAYER IS DISSOLVED, (C) BRINGING THE EXPOSED EMULSION LAYER OF THE NEGATIVE SHEET DURING DEVELOPMENT INTO CONTACT WITH AN AMOUNT OF DEVELOPMENT NUCLEI SUFFICIENT TO INCREASE THE ADHESIVENESS OF A TRANSFER SHEET TO THE EMULSION LAYER BUT AN AMOUNT LESS THAN THAT WHICH CAUSES A VISIBLE SILVER PRECIPITATION IN THE TRANSFER SHEET, SAID DEVELOPMENT NUCLEI BEING SELECTED FROM THE GROUP CONSISTING OF HEAVY METALS, HEAVY METAL SULFIDES AND HEAVY METAL SELENIDES AND INTO CONTACT WITH A TRANSFER SHEET, SAID TRANSFER SHEET CONSISTING ESSENTIALLY OF A TRANSFER LAYER OF A FILM-FORMING CARBOXYSUBSTITUTED CARBOHYDRATE HAVING A PYRANOSIDE STRUCTURE AND CONTAINING BETWEEN 10 AND 50 PERCENT BY WEIGHT CARBOXYL RADICALS ADHERING TO A TRANSFER SHEET SUPPORTING LAYER WHEREBY SILVER HALIDE DISSOLVED FROM THE UNEXPOSED AREAS OF THE EMULSION LAYER DIFFUSES IMAGEWISE INTO THE TRANSFER LAYER THEREBY INCREASING IMAGEWISE THE ADHESIVENESS OF THE TRANSFER LAYER TO THE EMULSION LAYER, AND (D) SEPARATING THE TRANSFER SHEET AND THE NEGATIVE SHEET WHEREBY THOSE PORTIONS OF THE TRANSFER LAYER WHICH WERE IN CONTACT WITH THE UNEXPOSED AREAS OF THE EMULSION LAYER NOW ADHERETO THE EMULSION LAYER AND THOSE PORTIONS OF THE TRANSFER LAYER WHICH WERE IN CONTACT WITH THE EXPOSED AREAS OF THE EMULSION LAYER REMAIN ADHERING TO THE TRANSFER SHEET SUPPORTING LAYER THEREBY PRODUCING (I) A POSITIVE LATERALLY REVERSED PRINTING FORM COMPRISING THE NEGATIVE SHEET AND A RELIEF LAYER OF PORTIONS OF THE TRANSFER LAYER AND (II) A NEGATIVE NON-LATERALLY REVERSED PRINTING FORM COMPRISING THE TRANSFER SHEET SUPPORTING LAYER AND A RELIEF LAYER OF THE REMAINING PORTION OF THE TRANSFER LAYER. 